Tetsuwan Birdy Decode - The Cipher is the intermission between the first and second seasons. This was released after the 2nd season aired. This 25 min OVA introduces us to some of the players central to the story of the 2nd season, gives us more of the characters we love, and rehashes an old short joke from the 1st season. I can't really go into details without spoiling anything, but it has a little bit of action, some sweet moments, and the occasional bit of comedy. The entire series just has this special charm about it, and this OVA is no exception. So if you enjoythe series at all this is a must see.